Based on the division of regions on Helan mountains,the vegetation changes of four seasons from 1998 to 2010 in different regions has been analyzed using the SPOT-NDVI data.The results shown that average vegetation cover was highest in high elevations and second highest in middle elevations,and then the low elevation areas.The vegetation cover on east slope of the study area was higher than the west slope,north part and south part of Helan mountains.The growth period of vegetation was from May to October,with the highest vegetation cover in August.The vegetation was generally getting better in the past 13 years,in which the vegetation grew better in autumn for most areas,especially in the middle and high elevations areas.However,considering the negative effects of the climatic arid trend on vegetation growth in the study area,the trend of vegetation grow would probably reverse in the future.

Wang Haijun1,Jin Xiaohua2,Li Hailong1,Zhang Bo3,Dai Shengpei3 (1. Engineering and Technical College of Chengdu University of Technology,Leshan 614007,China;2. Key Lab of Marine Remote Sensing Science and Marine Dynamic Information System Technology, State Oceanic Administration,Qingdao 266061,China;3. College of Geography and Environmental Science,Northwest Normal University,Lanzhou 730070,China);NDVI variation and coupling analysis with climate change in northwest of China based on GIS and RS[J];Transactions of the Chinese Society of Agricultural Engineering;2010-11